/*!
 * Copyright 2012, Chris Wanstrath
 * Released under the MIT License
 * https://github.com/defunkt/jquery-pjax
 */

(function ($) {

    // When called on a container with a selector, fetches the href with
    // ajax into the container or with the data-pjax attribute on the link
    // itself.
    //
    // Tries to make sure the back button and ctrl+click work the way
    // you'd expect.
    //
    // Exported as $.fn.pjax
    //
    // Accepts a jQuery ajax options object that may include these
    // pjax specific options:
    //
    //
    // container - Where to stick the response body. Usually a String selector.
    //             $(container).html(xhr.responseBody)
    //             (default: current jquery context)
    //      push - Whether to pushState the URL. Defaults to true (of course).
    //   replace - Want to use replaceState instead? That's cool.
    //
    // For convenience the second parameter can be either the container or
    // the options object.
    //
    // Returns the jQuery object
    function fnPjax(selector, container, options) {
        var context = this
        return this.on('click.pjax', selector, function(event) {
            var opts = $.extend({}, optionsFor(container, options));
            if (!opts.container)
                opts.container = $(this).attr('data-pjax') || context;
            handleClick(event, opts);
        });
    }

    // Public: pjax on click handler
    //
    // Exported as $.pjax.click.
    //
    // event   - "click" jQuery.Event
    // options - pjax options
    //
    // Examples
    //
    //   $(document).on('click', 'a', $.pjax.click)
    //   // is the same as
    //   $(document).pjax('a')
    //
    //  $(document).on('click', 'a', function(event) {
    //    var container = $(this).closest('[data-pjax-container]')
    //    $.pjax.click(event, container)
    //  })
    //
    // Returns nothing.
    function handleClick(event, container, options) {
        options = optionsFor(container, options)

        var link = event.currentTarget;

        if (link.tagName.toUpperCase() !== 'A')
            throw "$.fn.pjax or $.pjax.click requires an anchor element";

        // Middle click, cmd click, and ctrl click should open
        // links in a new tab as normal.
        if (event.which > 1 || event.metaKey || event.ctrlKey || event.shiftKey || event.altKey)
            return;

        // Ignore cross origin links
        if (location.protocol !== link.protocol || location.hostname !== link.hostname)
            return;

        // Ignore case when a hash is being tacked on the current URL
        if (link.href.indexOf('#') > -1 && stripHash(link) == stripHash(location))
            return;

        // Ignore event with default prevented
        if (event.isDefaultPrevented())
            return;

        var defaults = {
            url: link.href,
            container: $(link).attr('data-pjax'),
            target: link
        }

        var opts = $.extend({}, defaults, options);
        var clickEvent = $.Event('pjax:click');
        $(link).trigger(clickEvent, [opts]);

        if (!clickEvent.isDefaultPrevented()) {
            pjax(opts);
            event.preventDefault();
            $(link).trigger('pjax:clicked', [opts]);
        }
    }

    // Public: pjax on form submit handler
    //
    // Exported as $.pjax.submit
    //
    // event   - "click" jQuery.Event
    // options - pjax options
    //
    // Examples
    //
    //  $(document).on('submit', 'form', function(event) {
    //    var container = $(this).closest('[data-pjax-container]')
    //    $.pjax.submit(event, container)
    //  })
    //
    // Returns nothing.
    function handleSubmit(event, container, options) {
        options = optionsFor(container, options);

        var form = event.currentTarget;
        var $form = $(form);

        if (form.tagName.toUpperCase() !== 'FORM')
            throw "$.pjax.submit requires a form element";

        var defaults = {
            type: ($form.attr('method') || 'GET').toUpperCase(),
            url: $form.attr('action'),
            container: $form.attr('data-pjax'),
            target: form
        }

        if (defaults.type !== 'GET' && window.FormData !== undefined) {
            defaults.data = new FormData(form);
            defaults.processData = false;
            defaults.contentType = false;
        } else {
            // Can't handle file uploads, exit
            if ($(form).find(':file').length) {
                return;
            }

            // Fallback to manually serializing the fields
            defaults.data = $(form).serializeArray();
        }

        pjax($.extend({}, defaults, options));

        event.preventDefault();
    }

    // Loads a URL with ajax, puts the response body inside a container,
    // then pushState()'s the loaded URL.
    //
    // Works just like $.ajax in that it accepts a jQuery ajax
    // settings object (with keys like url, type, data, etc).
    //
    // Accepts these extra keys:
    //
    // container - Where to stick the response body.
    //             $(container).html(xhr.responseBody)
    //      push - Whether to pushState the URL. Defaults to true (of course).
    //   replace - Want to use replaceState instead? That's cool.
    //
    // Use it just like $.ajax:
    //
    //   var xhr = $.pjax({ url: this.href, container: '#main' })
    //   console.log( xhr.readyState )
    //
    // Returns whatever $.ajax returns.
    function pjax(options) {
        options = $.extend(true, {}, $.ajaxSettings, pjax.defaults, options);

        if ($.isFunction(options.url)) {
            options.url = options.url();
        }

        var target = options.target;

        var hash = parseURL(options.url).hash;

        var context = options.context = findContainerFor(options.container);

        // We want the browser to maintain two separate internal caches: one
        // for pjax'd partial page loads and one for normal page loads.
        // Without adding this secret parameter, some browsers will often
        // confuse the two.
        if (!options.data) options.data = {}
        if ($.isArray(options.data)) {
            options.data.push({ name: '_pjax', value: context.selector });
        } else {
            options.data._pjax = context.selector;
        }

        function fire(type, args, props) {
            if (!props) props = {}
            props.relatedTarget = target;
            var event = $.Event(type, props);
            context.trigger(event, args);
            return !event.isDefaultPrevented();
        }

        var timeoutTimer;

        options.beforeSend = function (xhr, settings) {
            // No timeout for non-GET requests
            // Its not safe to request the resource again with a fallback method.
            if (settings.type !== 'GET') {
                settings.timeout = 0;
            }

            xhr.setRequestHeader('X-PJAX', 'true');
            xhr.setRequestHeader('X-PJAX-Container', context.selector);

            if (!fire('pjax:beforeSend', [xhr, settings]))
                return false;

            if (settings.timeout > 0) {
                timeoutTimer = setTimeout(function () {
                    if (fire('pjax:timeout', [xhr, options]))
                        xhr.abort('timeout');
                }, settings.timeout);

                // Clear timeout setting so jquerys internal timeout isn't invoked
                settings.timeout = 0;
            }

            var url = parseURL(settings.url);
            if (hash) url.hash = hash;
            options.requestUrl = stripInternalParams(url);
        }

        options.complete = function (xhr, textStatus) {
            if (timeoutTimer)
                clearTimeout(timeoutTimer);

            fire('pjax:complete', [xhr, textStatus, options]);

            fire('pjax:end', [xhr, options]);
        }

        options.error = function (xhr, textStatus, errorThrown) {
            var container = extractContainer("", xhr, options);

            var allowed = fire('pjax:error', [xhr, textStatus, errorThrown, options]);
            if (options.type == 'GET' && textStatus !== 'abort' && allowed) {
                locationReplace(container.url);
            }
        }

        options.success = function (data, status, xhr) {
            var previousState = pjax.state;

            // If $.pjax.defaults.version is a function, invoke it first.
            // Otherwise it can be a static string.
            var currentVersion = (typeof $.pjax.defaults.version === 'function') ?
              $.pjax.defaults.version() :
              $.pjax.defaults.version;

            var latestVersion = xhr.getResponseHeader('X-PJAX-Version');

            var container = extractContainer(data, xhr, options);

            var url = parseURL(container.url);
            if (hash) {
                url.hash = hash;
                container.url = url.href;
            }

            // If there is a layout version mismatch, hard load the new url
            if (currentVersion && latestVersion && currentVersion !== latestVersion) {
                locationReplace(container.url);
                return;
            }

            // If the new response is missing a body, hard load the page
            if (!container.contents) {
                locationReplace(container.url);
                return;
            }

            pjax.state = {
                id: options.id || uniqueId(),
                url: container.url,
                title: container.title,
                container: context.selector,
                fragment: options.fragment,
                timeout: options.timeout
            }

            if (options.push || options.replace) {
                window.history.replaceState(pjax.state, container.title, container.url);
            }

            // Only blur the focus if the focused element is within the container.
            var blurFocus = $.contains(options.container, document.activeElement);

            // Clear out any focused controls before inserting new page contents.
            if (blurFocus) {
                try {
                    document.activeElement.blur();
                } catch (e) { }
            }

            if (container.title) document.title = container.title;

            fire('pjax:beforeReplace', [container.contents, options], {
                state: pjax.state,
                previousState: previousState
            });
            context.html(container.contents);

            // FF bug: Won't autofocus fields that are inserted via JS.
            // This behavior is incorrect. So if theres no current focus, autofocus
            // the last field.
            //
            // http://www.w3.org/html/wg/drafts/html/master/forms.html
            var autofocusEl = context.find('input[autofocus], textarea[autofocus]').last()[0];
            if (autofocusEl && document.activeElement !== autofocusEl) {
                autofocusEl.focus();
            }

            executeScriptTags(container.scripts);

            var scrollTo = options.scrollTo;

            // Ensure browser scrolls to the element referenced by the URL anchor
            if (hash) {
                var name = decodeURIComponent(hash.slice(1));
                var target = document.getElementById(name) || document.getElementsByName(name)[0];
                if (target) scrollTo = $(target).offset().top;
            }

            if (typeof scrollTo == 'number') $(window).scrollTop(scrollTo);

            fire('pjax:success', [data, status, xhr, options]);
        }


        // Initialize pjax.state for the initial page load. Assume we're
        // using the container and options of the link we're loading for the
        // back button to the initial page. This ensures good back button
        // behavior.
        if (!pjax.state) {
            pjax.state = {
                id: uniqueId(),
                url: window.location.href,
                title: document.title,
                container: context.selector,
                fragment: options.fragment,
                timeout: options.timeout
            }
            window.history.replaceState(pjax.state, document.title)
        }

        // Cancel the current request if we're already pjaxing
        abortXHR(pjax.xhr);

        pjax.options = options;
        var xhr = pjax.xhr = $.ajax(options);

        if (xhr.readyState > 0) {
            if (options.push && !options.replace) {
                // Cache current container element before replacing it
                cachePush(pjax.state.id, cloneContents(context));

                window.history.pushState(null, "", options.requestUrl);
            }

            fire('pjax:start', [xhr, options]);
            fire('pjax:send', [xhr, options]);
        }

        return pjax.xhr;
    }

    // Public: Reload current page with pjax.
    //
    // Returns whatever $.pjax returns.
    function pjaxReload(container, options) {
        var defaults = {
            url: window.location.href,
            push: false,
            replace: true,
            scrollTo: false
        }

        return pjax($.extend(defaults, optionsFor(container, options)));
    }

    // Internal: Hard replace current state with url.
    //
    // Work for around WebKit
    //   https://bugs.webkit.org/show_bug.cgi?id=93506
    //
    // Returns nothing.
    function locationReplace(url) {
        window.history.replaceState(null, "", pjax.state.url);
        window.location.replace(url);
    }


    var initialPop = true;
    var initialURL = window.location.href;
    var initialState = window.history.state;

    // Initialize $.pjax.state if possible
    // Happens when reloading a page and coming forward from a different
    // session history.
    if (initialState && initialState.container) {
        pjax.state = initialState;
    }

    // Non-webkit browsers don't fire an initial popstate event
    if ('state' in window.history) {
        initialPop = false;
    }

    // popstate handler takes care of the back and forward buttons
    //
    // You probably shouldn't use pjax on pages with other pushState
    // stuff yet.
    function onPjaxPopstate(event) {

        // Hitting back or forward should override any pending PJAX request.
        if (!initialPop) {
            abortXHR(pjax.xhr);
        }

        var previousState = pjax.state;
        var state = event.state;
        var direction;

        if (state && state.container) {
            // When coming forward from a separate history session, will get an
            // initial pop with a state we are already at. Skip reloading the current
            // page.
            if (initialPop && initialURL == state.url) return;

            if (previousState) {
                // If popping back to the same state, just skip.
                // Could be clicking back from hashchange rather than a pushState.
                if (previousState.id === state.id) return;

                // Since state IDs always increase, we can deduce the navigation direction
                direction = previousState.id < state.id ? 'forward' : 'back';
            }

            var cache = cacheMapping[state.id] || [];
            var container = $(cache[0] || state.container), contents = cache[1];

            if (container.length) {
                if (previousState) {
                    // Cache current container before replacement and inform the
                    // cache which direction the history shifted.
                    cachePop(direction, previousState.id, cloneContents(container));
                }

                var popstateEvent = $.Event('pjax:popstate', {
                    state: state,
                    direction: direction
                });
                container.trigger(popstateEvent);

                var options = {
                    id: state.id,
                    url: state.url,
                    container: container,
                    push: false,
                    fragment: state.fragment,
                    timeout: state.timeout,
                    scrollTo: false
                }

                if (contents) {
                    container.trigger('pjax:start', [null, options]);

                    pjax.state = state;
                    if (state.title) document.title = state.title;
                    var beforeReplaceEvent = $.Event('pjax:beforeReplace', {
                        state: state,
                        previousState: previousState
                    });
                    container.trigger(beforeReplaceEvent, [contents, options]);
                    container.html(contents);

                    container.trigger('pjax:end', [null, options]);
                } else {
                    pjax(options);
                }

                // Force reflow/relayout before the browser tries to restore the
                // scroll position.
                container[0].offsetHeight;
            } else {
                locationReplace(location.href);
            }
        }
        initialPop = false;
    }

    // Fallback version of main pjax function for browsers that don't
    // support pushState.
    //
    // Returns nothing since it retriggers a hard form submission.
    function fallbackPjax(options) {
        var url = $.isFunction(options.url) ? options.url() : options.url,
            method = options.type ? options.type.toUpperCase() : 'GET';

        var form = $('<form>', {
            method: method === 'GET' ? 'GET' : 'POST',
            action: url,
            style: 'display:none'
        });

        if (method !== 'GET' && method !== 'POST') {
            form.append($('<input>', {
                type: 'hidden',
                name: '_method',
                value: method.toLowerCase()
            }));
        }

        var data = options.data;
        if (typeof data === 'string') {
            $.each(data.split('&'), function (index, value) {
                var pair = value.split('=');
                form.append($('<input>', { type: 'hidden', name: pair[0], value: pair[1] }));
            });
        } else if ($.isArray(data)) {
            $.each(data, function (index, value) {
                form.append($('<input>', { type: 'hidden', name: value.name, value: value.value }));
            });
        } else if (typeof data === 'object') {
            var key
            for (key in data)
                form.append($('<input>', { type: 'hidden', name: key, value: data[key] }));
        }

        $(document.body).append(form);
        form.submit();
    }

    // Internal: Abort an XmlHttpRequest if it hasn't been completed,
    // also removing its event handlers.
    function abortXHR(xhr) {
        if (xhr && xhr.readyState < 4) {
            xhr.onreadystatechange = $.noop;
            xhr.abort();
        }
    }

    // Internal: Generate unique id for state object.
    //
    // Use a timestamp instead of a counter since ids should still be
    // unique across page loads.
    //
    // Returns Number.
    function uniqueId() {
        return (new Date).getTime();
    }

    function cloneContents(container) {
        var cloned = container.clone()
        // Unmark script tags as already being eval'd so they can get executed again
        // when restored from cache. HAXX: Uses jQuery internal method.
        cloned.find('script').each(function () {
            if (!this.src) jQuery._data(this, 'globalEval', false);
        });
        return [container.selector, cloned.contents()];
    }

    // Internal: Strip internal query params from parsed URL.
    //
    // Returns sanitized url.href String.
    function stripInternalParams(url) {
        url.search = url.search.replace(/([?&])(_pjax|_)=[^&]*/g, '');
        return url.href.replace(/\?($|#)/, '$1');
    }

    // Internal: Parse URL components and returns a Locationish object.
    //
    // url - String URL
    //
    // Returns HTMLAnchorElement that acts like Location.
    function parseURL(url) {
        var a = document.createElement('a');
        a.href = url;
        return a;
    }

    // Internal: Return the `href` component of given URL object with the hash
    // portion removed.
    //
    // location - Location or HTMLAnchorElement
    //
    // Returns String
    function stripHash(location) {
        return location.href.replace(/#.*/, '');
    }

    // Internal: Build options Object for arguments.
    //
    // For convenience the first parameter can be either the container or
    // the options object.
    //
    // Examples
    //
    //   optionsFor('#container')
    //   // => {container: '#container'}
    //
    //   optionsFor('#container', {push: true})
    //   // => {container: '#container', push: true}
    //
    //   optionsFor({container: '#container', push: true})
    //   // => {container: '#container', push: true}
    //
    // Returns options Object.
    function optionsFor(container, options) {
        // Both container and options
        if (container && options)
            options.container = container;

            // First argument is options Object
        else if ($.isPlainObject(container))
            options = container;

            // Only container
        else
            options = { container: container }

        // Find and validate container
        if (options.container)
            options.container = findContainerFor(options.container);

        return options;
    }

    // Internal: Find container element for a variety of inputs.
    //
    // Because we can't persist elements using the history API, we must be
    // able to find a String selector that will consistently find the Element.
    //
    // container - A selector String, jQuery object, or DOM Element.
    //
    // Returns a jQuery object whose context is `document` and has a selector.
    function findContainerFor(container) {
        container = $(container);

        if (!container.length) {
            throw "no pjax container for " + container.selector;
        } else if (container.selector !== '' && container.context === document) {
            return container;
        } else if (container.attr('id')) {
            return $('#' + container.attr('id'));
        } else {
            throw "cant get selector for pjax container!";
        }
    }

    // Internal: Filter and find all elements matching the selector.
    //
    // Where $.fn.find only matches descendants, findAll will test all the
    // top level elements in the jQuery object as well.
    //
    // elems    - jQuery object of Elements
    // selector - String selector to match
    //
    // Returns a jQuery object.
    function findAll(elems, selector) {
        return elems.filter(selector).add(elems.find(selector));
    }

    function parseHTML(html) {
        return $.parseHTML(html, document, true);
    }

    // Internal: Extracts container and metadata from response.
    //
    // 1. Extracts X-PJAX-URL header if set
    // 2. Extracts inline <title> tags
    // 3. Builds response Element and extracts fragment if set
    //
    // data    - String response data
    // xhr     - XHR response
    // options - pjax options Object
    //
    // Returns an Object with url, title, and contents keys.
    function extractContainer(data, xhr, options) {
        var obj = {}, fullDocument = /<html/i.test(data);

        // Prefer X-PJAX-URL header if it was set, otherwise fallback to
        // using the original requested url.
        var serverUrl = xhr.getResponseHeader('X-PJAX-URL');
        obj.url = serverUrl ? stripInternalParams(parseURL(serverUrl)) : options.requestUrl;

        // Attempt to parse response html into elements
        if (fullDocument) {
            var $head = $(parseHTML(data.match(/<head[^>]*>([\s\S.]*)<\/head>/i)[0]));
            var $body = $(parseHTML(data.match(/<body[^>]*>([\s\S.]*)<\/body>/i)[0]));
        } else {
            var $head = $body = $(parseHTML(data));
        }

        // If response data is empty, return fast
        if ($body.length === 0)
            return obj

        // If there's a <title> tag in the header, use it as
        // the page's title.
        obj.title = findAll($head, 'title').last().text();

        if (options.fragment) {
            // If they specified a fragment, look for it in the response
            // and pull it out.
            if (options.fragment === 'body') {
                var $fragment = $body;
            } else {
                var $fragment = findAll($body, options.fragment).first();
            }

            if ($fragment.length) {
                obj.contents = options.fragment === 'body' ? $fragment : $fragment.contents();

                // If there's no title, look for data-title and title attributes
                // on the fragment
                if (!obj.title)
                    obj.title = $fragment.attr('title') || $fragment.data('title');
            }

        } else if (!fullDocument) {
            obj.contents = $body;
        }

        // Clean up any <title> tags
        if (obj.contents) {
            // Remove any parent title elements
            obj.contents = obj.contents.not(function () { return $(this).is('title') });

            // Then scrub any titles from their descendants
            obj.contents.find('title').remove();

            // Gather all script[src] elements
            obj.scripts = findAll(obj.contents, 'script[src]').remove();
            obj.contents = obj.contents.not(obj.scripts);
        }

        // Trim any whitespace off the title
        if (obj.title) obj.title = $.trim(obj.title);

        return obj;
    }

    // Load an execute scripts using standard script request.
    //
    // Avoids jQuery's traditional $.getScript which does a XHR request and
    // globalEval.
    //
    // scripts - jQuery object of script Elements
    //
    // Returns nothing.
    function executeScriptTags(scripts) {
        if (!scripts) return;

        var existingScripts = $('script[src]');

        scripts.each(function () {
            var src = this.src;
            var matchedScripts = existingScripts.filter(function () {
                return this.src === src;
            });
            if (matchedScripts.length) return

            var script = document.createElement('script');
            var type = $(this).attr('type');
            if (type) script.type = type;
            script.src = $(this).attr('src');
            document.head.appendChild(script);
        });
    }

    // Internal: History DOM caching class.
    var cacheMapping = {}
    var cacheForwardStack = [];
    var cacheBackStack = [];

    // Push previous state id and container contents into the history
    // cache. Should be called in conjunction with `pushState` to save the
    // previous container contents.
    //
    // id    - State ID Number
    // value - DOM Element to cache
    //
    // Returns nothing.
    function cachePush(id, value) {
        cacheMapping[id] = value;
        cacheBackStack.push(id);

        // Remove all entries in forward history stack after pushing a new page.
        trimCacheStack(cacheForwardStack, 0);

        // Trim back history stack to max cache length.
        trimCacheStack(cacheBackStack, pjax.defaults.maxCacheLength);
    }

    // Shifts cache from directional history cache. Should be
    // called on `popstate` with the previous state id and container
    // contents.
    //
    // direction - "forward" or "back" String
    // id        - State ID Number
    // value     - DOM Element to cache
    //
    // Returns nothing.
    function cachePop(direction, id, value) {
        var pushStack, popStack;
        cacheMapping[id] = value;

        if (direction === 'forward') {
            pushStack = cacheBackStack;
            popStack = cacheForwardStack;
        } else {
            pushStack = cacheForwardStack;
            popStack = cacheBackStack;
        }

        pushStack.push(id);
        if (id = popStack.pop())
            delete cacheMapping[id]

        // Trim whichever stack we just pushed to to max cache length.
        trimCacheStack(pushStack, pjax.defaults.maxCacheLength);
    }

    // Trim a cache stack (either cacheBackStack or cacheForwardStack) to be no
    // longer than the specified length, deleting cached DOM elements as necessary.
    //
    // stack  - Array of state IDs
    // length - Maximum length to trim to
    //
    // Returns nothing.
    function trimCacheStack(stack, length) {
        while (stack.length > length)
            delete cacheMapping[stack.shift()]
    }

    // Public: Find version identifier for the initial page load.
    //
    // Returns String version or undefined.
    function findVersion() {
        return $('meta').filter(function() {
            var name = $(this).attr('http-equiv');
            return name && name.toUpperCase() === 'X-PJAX-VERSION';
        }).attr('content');
    }

    // Install pjax functions on $.pjax to enable pushState behavior.
    //
    // Does nothing if already enabled.
    //
    // Examples
    //
    //     $.pjax.enable()
    //
    // Returns nothing.
    function enable() {
        $.fn.pjax = fnPjax;
        $.pjax = pjax;
        $.pjax.enable = $.noop;
        $.pjax.disable = disable;
        $.pjax.click = handleClick;
        $.pjax.submit = handleSubmit;
        $.pjax.reload = pjaxReload;
        $.pjax.defaults = {
            timeout: 650,
            push: true,
            replace: false,
            type: 'GET',
            dataType: 'html',
            scrollTo: 0,
            maxCacheLength: 20,
            version: findVersion
        }
        $(window).on('popstate.pjax', onPjaxPopstate);
    }

    // Disable pushState behavior.
    //
    // This is the case when a browser doesn't support pushState. It is
    // sometimes useful to disable pushState for debugging on a modern
    // browser.
    //
    // Examples
    //
    //     $.pjax.disable()
    //
    // Returns nothing.
    function disable() {
        $.fn.pjax = function () { return this }
        $.pjax = fallbackPjax;
        $.pjax.enable = enable;
        $.pjax.disable = $.noop;
        $.pjax.click = $.noop;
        $.pjax.submit = $.noop;
        $.pjax.reload = function () { window.location.reload() }

        $(window).off('popstate.pjax', onPjaxPopstate);
    }


    // Add the state property to jQuery's event object so we can use it in
    // $(window).bind('popstate')
    if ($.inArray('state', $.event.props) < 0)
        $.event.props.push('state')

    // Is pjax supported by this browser?
    $.support.pjax =
      window.history && window.history.pushState && window.history.replaceState &&
      // pushState isn't reliable on iOS until 5.
      !navigator.userAgent.match(/((iPod|iPhone|iPad).+\bOS\s+[1-4]\D|WebApps\/.+CFNetwork)/)

    $.support.pjax ? enable() : disable()

})(jQuery);
